Solution : If you want to factory reset ABB DCS550 drive parameter then use the following step :

1. First take drive in local mode by pressing LOC/REM button.

2. Press enter button and select PARAMETER and then press enter button & goto the parameter group 99.

3. After enter select parameter 99.08 set value 1 (Factory) and then press enter button to save.

now your drive reset to the factory default.